According to a known conventional control system, such as the one disclosed in the Japanese Application Patent Laid-Open Publication No. Hei 10-3409 (1998), fail-safe function has been maintained in such a manner that, when the microcomputer goes out of control and no watchdog signal is outputted, the monitor IC judges the microcomputer is out of control and outputs a mask signal, and immediately stops outputting control signals to the devices under control.